Fish, prawn, lobster or shrimp husbandry under a controlled environment, sometimes referred to as aquaculture, offers numerous advantages which are by now well known. Some of these advantages are the ability to provide large quantities of good quality high protein food at relatively low cost, the opportunity to regularize the supply of gourmet fish subject in nature to seasonal fluctuations and the ability to conduct operations at inland locations thereby increasing the availability of fish and crustaceans to residents located far from the coastline.
Such commercial potential has stimulated interest in aquaculture and it has been discovered experimentally that confined fish under continuous visual monitoring of feeding activity can convert 0.9 pounds of dry feed to 1.0 pounds of fresh fish. These laboratory results are not, however, experienced at commercial fish farms. Because of the inability to monitor feeding activity of species which typically bottom feed, a feed conversion ratio of 1.9 pounds of dry feed to 1.0 pounds of fresh fish is considered an excellent commercial result. Since the cost of the feed typically represents more than one half of the cost of the fish husbandry, it would be very advantageous to improve the feed conversion ratio by directly monitoring feeding activity and only feeding the culture to satiation.
Despite the economic importance of the feed conversion ratio, currently known fish farming methods do not include a process for quantitatively monitoring the food actually consumed by the culture. When fish will feed at the surface, the farmer can observe the crop regularly and gain some sense of survival and growth, especially if a floating food pellet is used to encourage surface feeding. However, many commercially useful species such as shrimp, prawns, lobsters and catfish feed slowly and continuously and require a sinking feed with considerable stability when submerged. For these cases, the amount of feed required is an educated guess and wasted feed is the primary cause of poor conversion in commercial aquacultures.
Excess food accumulation also depletes oxygen since oxygen in water is consumed in the decomposition of wasted food. Numerous methods are employed to remove the food through suction sweepers and flow through of water in order to prevent disease and death of the culture. These are expensive and do little to improve feed conversion ratio.
Problems of a similar nature are experienced in the raising of tropical fish where it often becomes necessary for the owner to be away from the aquarium for an extended period of time. During this time it is necessary to feed the fish to keep them alive. Previously known processes have employed timing structures which dispense food at intervals largely unrelated to the actual consumption of the food. Overfeeding or underfeeding over periods of weeks has resulted in loss of expensive fish. Currently known methods do not include a method for determining whether food administered to an aquarium is actually being eaten and for using this information to vary the amount of food administered to suit the long-term needs of the aquarium.
It is an object of the invention to overcome the objections to the proir art processes and provide a simple method for monitoring the consumption of food by aquatic creatures, especially fish and crustaceans, and thereby provide the information necessary for varing the amount of food administered periodically to said creatures for their optimum health and growth.
It is a further object of the invention to provide a sensitive indicator of whether a culture has been fed to satiation and to thereby reduce the amount of feed typically wasted during the feeding of aquacultures.